"89 4WS Prelude funny engine

[loopyloo]

I had the idea of buying this other Prelude for spares for my current Prelude.
The engine has a strange problem and I was hoping someone might know the cause before I go ahead and buy it.

It's the BA4 2 litre engine coupled to automatic transmission.
The guy started it and it run fairly normal for a few minutes until I decided to hop in and blip the throttle.
Immediately, it started this auto revving thing where it would go from idle to 1600 revs slowly then drop back to idle then repeat continuously. It kept doing this for the rest of the time the engine was running.
Each revving cycle from idle to 1600 and back to idle to immediately start the cycle again was about 2 seconds.

The guy said something about "oh that 's the speedo cable again", but I he didn't know what he was talking about and apparently someone told him about the cable.

Any thoughts anyone ??

Loopyloo

[Godzilla]

Starting points....

Vacuum leak
Faulty throttle position switch
Faulty idle bypass/control valve.
Some cars have a idle speed motor that can play games.
Dirty throttle body.
Airlock in coolant.

Id aim to clean the throttle body and idle valve first and bleed the cooling system, costs nothing...

[carjackma]

I had the idea of buying this other Prelude for spares for my current Prelude.
The engine has a strange problem and I was hoping someone might know the cause before I go ahead and buy it.

It's the BA4 2 litre engine coupled to automatic transmission.
The guy started it and it run fairly normal for a few minutes until I decided to hop in and blip the throttle.
Immediately, it started this auto revving thing where it would go from idle to 1600 revs slowly then drop back to idle then repeat continuously. It kept doing this for the rest of the time the engine was running.
Each revving cycle from idle to 1600 and back to idle to immediately start the cycle again was about 2 seconds.

The guy said something about "oh that 's the speedo cable again", but I he didn't know what he was talking about and apparently someone told him about the cable.

Any thoughts anyone ??

Loopyloo

its a honda and that problem is a common one its the IAC valve replace it and all will be well

[polarbear]

its a honda and that problem is a common one its the IAC valve replace it and all will be well

I think carjackma could be right on the money here, Just did a quick google search on Idle Air Control valve & Honda and it then found some You tube videos re Honda engines with your cars problem/symptoms described and how to repair the problem - Video clip below might be of some help to you, Good luck

[ame=http://www.youtube.com/watch?v=tUkCCwqU3eU]How to Clean the IACV- Idle Air Control Valve - YouTube[/ame]

[loopyloo]

Excellent...Thanks guys.
Yeah found it in the manual now you've mentioned it, where they call it an EACV.
Sounds highly likely to be the suspect. I'll check it out.

Loopy.

[Tradesman]

wonder what the part would cost? look for an aftermarket one may be cheaper